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Date:   Tue, 16 Jan 2018 14:50:34 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Jon Maloy <jon.maloy@...csson.com>
Cc:     Cong Wang <xiyou.wangcong@...il.com>,
        syzbot <syzbot+799dafde0286795858ac@...kaller.appspotmail.com>,
        David Miller <davem@...emloft.net>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        "syzkaller-bugs@...glegroups.com" <syzkaller-bugs@...glegroups.com>,
        "tipc-discussion@...ts.sourceforge.net" 
        <tipc-discussion@...ts.sourceforge.net>,
        Ying Xue <ying.xue@...driver.com>
Subject: Re: KASAN: use-after-free Read in tipc_group_is_open

On Tue, Jan 16, 2018 at 2:23 PM, Jon Maloy <jon.maloy@...csson.com> wrote:
>
>
>> -----Original Message-----
>> From: Cong Wang [mailto:xiyou.wangcong@...il.com]
>> Sent: Monday, January 15, 2018 23:44
>> To: syzbot <syzbot+799dafde0286795858ac@...kaller.appspotmail.com>
>> Cc: David Miller <davem@...emloft.net>; Jon Maloy
>> <jon.maloy@...csson.com>; LKML <linux-kernel@...r.kernel.org>; Linux
>> Kernel Network Developers <netdev@...r.kernel.org>; syzkaller-
>> bugs@...glegroups.com; tipc-discussion@...ts.sourceforge.net; Ying Xue
>> <ying.xue@...driver.com>
>> Subject: Re: KASAN: use-after-free Read in tipc_group_is_open
>>
>> On Mon, Jan 15, 2018 at 7:58 PM, syzbot
>> <syzbot+799dafde0286795858ac@...kaller.appspotmail.com> wrote:
>> > Hello,
>> >
>> > syzkaller hit the following crash on
>> > 594831a8aba3fd045c3212a3e3bb9788c77b989d
>> > git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/maste
>> > r
>> > compiler: gcc (GCC) 7.1.1 20170620
>> > .config is attached
>> > Raw console output is attached.
>> > C reproducer is attached
>> > syzkaller reproducer is attached. See https://goo.gl/kgGztJ for
>> > information about syzkaller reproducers
>> >
>> >
>> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> > Reported-by: syzbot+799dafde0286795858ac@...kaller.appspotmail.com
>> > It will help syzbot understand when the bug is fixed. See footer for
>> > details.
>> > If you forward the report, please keep this part and the footer.
>> >
>> >
>> ==========================================================
>> ========
>> > BUG: KASAN: use-after-free in tipc_group_is_open+0x3a/0x40
>> > net/tipc/group.c:106
>> > Read of size 1 at addr ffff8801d89f7378 by task syzkaller275009/3704
>> >
>> > CPU: 0 PID: 3704 Comm: syzkaller275009 Not tainted 4.15.0-rc7+ #190
>> > Hardware name: Google Google Compute Engine/Google Compute Engine,
>> > BIOS Google 01/01/2011 Call Trace:
>> >  __dump_stack lib/dump_stack.c:17 [inline]
>> >  dump_stack+0x194/0x257 lib/dump_stack.c:53
>> >  print_address_description+0x73/0x250 mm/kasan/report.c:252
>> > kasan_report_error mm/kasan/report.c:351 [inline]
>> >  kasan_report+0x25b/0x340 mm/kasan/report.c:409
>> >  __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:427
>> >  tipc_group_is_open+0x3a/0x40 net/tipc/group.c:106
>> >  tipc_poll+0x364/0x4d0 net/tipc/socket.c:740
>>
>>
>> commit eb929a91b213d2a72c5a8b4af9a1acf63bfb8287
>> Author: Jon Maloy <jon.maloy@...csson.com>
>> Date:   Mon Jan 8 21:03:31 2018 +0100
>>
>>     tipc: improve poll() for group member socket
>>
>> Apparently Jon's commit doesn't fix this. I also don't understand why Jon
>> believes sock_poll_wait() could sync with setsockopt path...
>
> While sock_poll_wait() is sleeping, it is possible that the item the 'grp' stack variable is pointing to might be deleted, invalidating the pointer.
> This is why I moved the initialization of the pointer to after sock_poll_wait().
> However, now tipc_sock->group is clearly set to NULL at both locations where a group item might be deleted, so the reason for the warning must be something else.
> I am open to suggestions.


FWIW it seems that malloc/free happened within the same syscall when
tipc_sk_publish() in tipc_sk_join() failed. Yet another thread somehow
referenced that object. Was it ever published?



>> >  sock_poll+0x141/0x320 net/socket.c:1111  do_pollfd fs/select.c:822
>> > [inline]  do_poll fs/select.c:872 [inline]
>> >  do_sys_poll+0x715/0x10b0 fs/select.c:966  SYSC_poll fs/select.c:1024
>> > [inline]
>> >  SyS_poll+0x10d/0x450 fs/select.c:1012
>> > entry_SYSCALL_64_fastpath+0x23/0x9a
>> > RIP: 0033:0x446129
>> > RSP: 002b:00007f0f2df96db8 EFLAGS: 00000246 ORIG_RAX:
>> 0000000000000007
>> > RAX: ffffffffffffffda RBX: 00000000006dbc54 RCX: 0000000000446129
>> > RDX: 0000000000007fff RSI: 000000000000000a RDI: 0000000020ef5000
>> > RBP: 00000000006dbc50 R08: 0000000000000000 R09: 0000000000000000
>> > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
>> > R13: 00007ffc07e2923f R14: 00007f0f2df979c0 R15: 0000000000000007
>> >
>> > Allocated by task 3702:
>> >  save_stack+0x43/0xd0 mm/kasan/kasan.c:447  set_track
>> > mm/kasan/kasan.c:459 [inline]
>> >  kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
>> >  kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3610  kmalloc
>> > include/linux/slab.h:499 [inline]  kzalloc include/linux/slab.h:688
>> > [inline]
>> >  tipc_group_create+0x144/0x900 net/tipc/group.c:180  tipc_sk_join
>> > net/tipc/socket.c:2762 [inline]
>> >  tipc_setsockopt+0x274/0xce0 net/tipc/socket.c:2877  SYSC_setsockopt
>> > net/socket.c:1823 [inline]
>> >  SyS_setsockopt+0x189/0x360 net/socket.c:1802
>> > entry_SYSCALL_64_fastpath+0x23/0x9a
>> >
>> > Freed by task 3702:
>> >  save_stack+0x43/0xd0 mm/kasan/kasan.c:447  set_track
>> > mm/kasan/kasan.c:459 [inline]
>> >  kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524  __cache_free
>> > mm/slab.c:3488 [inline]
>> >  kfree+0xd6/0x260 mm/slab.c:3803
>> >  tipc_group_delete+0x2c8/0x3d0 net/tipc/group.c:234  tipc_sk_join
>> > net/tipc/socket.c:2775 [inline]
>> >  tipc_setsockopt+0xaa9/0xce0 net/tipc/socket.c:2877  SYSC_setsockopt
>> > net/socket.c:1823 [inline]
>> >  SyS_setsockopt+0x189/0x360 net/socket.c:1802
>> > entry_SYSCALL_64_fastpath+0x23/0x9a
>> >
>> > The buggy address belongs to the object at ffff8801d89f7300  which
>> > belongs to the cache kmalloc-128 of size 128 The buggy address is
>> > located 120 bytes inside of  128-byte region [ffff8801d89f7300,
>> > ffff8801d89f7380) The buggy address belongs to the page:
>> > page:ffffea0007627dc0 count:1 mapcount:0 mapping:ffff8801d89f7000
>> > index:0x0
>> > flags: 0x2fffc0000000100(slab)
>> > raw: 02fffc0000000100 ffff8801d89f7000 0000000000000000
>> > 0000000100000015
>> > raw: ffffea0007622720 ffffea0007627ce0 ffff8801dac00640
>> > 0000000000000000 page dumped because: kasan: bad access detected
>> >
>> > Memory state around the buggy address:
>> >  ffff8801d89f7200: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>> >  ffff8801d89f7280: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>> >>
>> >> ffff8801d89f7300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> >
>> >                                                                 ^
>> >  ffff8801d89f7380: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
>> >  ffff8801d89f7400: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
>> >
>> ==========================================================
>> ========
>> >
>> >
>> > ---
>> > This bug is generated by a dumb bot. It may contain errors.
>> > See https://goo.gl/tpsmEJ for details.
>> > Direct all questions to syzkaller@...glegroups.com.
>> >
>> > syzbot will keep track of this bug report.
>> > If you forgot to add the Reported-by tag, once the fix for this bug is
>> > merged into any tree, please reply to this email with:
>> > #syz fix: exact-commit-title
>> > If you want to test a patch for this bug, please reply with:
>> > #syz test: git://repo/address.git branch and provide the patch inline
>> > or as an attachment.
>> > To mark this as a duplicate of another syzbot report, please reply with:
>> > #syz dup: exact-subject-of-another-report If it's a one-off invalid
>> > bug report, please reply with:
>> > #syz invalid
>> > Note: if the crash happens again, it will cause creation of a new bug
>> > report.
>> > Note: all commands must start from beginning of the line in the email body.
>
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